The present invention relates to automotive emission catalysts and specifically relates to a thermally stable high surface area catalyst carrier useful for supporting oxidation and/or reduction catalysts at elevated temperatures.
It is known that catalyst carrier materials for automotive emissions use should possess high surface area, refractoriness, and thermal stability. High surface area in the carrier increases catalyst dispersion which retards activity loss resulting from catalyst agglomeration and sintering, and increases the accessible catalyst surface area.
A wide variety of refractory metal oxides and metal oxide mixtures have been utilized to support noble metal and base metal catalysts, including alumina, silica, magnesia, titania, zirconia, and mixtures thereof. Many of these exhibit substantially reduced surface areas following exposure to temperatures in the 800.degree. C. range. We have found that the catalysts resulting from use of our invention are effective over the entire 50,000 mile test schedule specified by Federal Government Regulations and thus indicate resistance to poisoning by sulfur, phosphorus and lead found in an engine exhaust stream. Thus we are able to place the noble metal catalyst materials at the surface of the support as distinguished from other techniques which place the catalyst materials interior of the surface for protection from poisoning as disclosed in U.S. Pat. Nos. 4,128,506 and 4,152,301 and 4,153,579 issued to Summers and Hegedus on Dec. 5, 1978, May 1, 1979, and May 8, 1979, respectively.